1. Field of the Invention
The subject matter disclosed generally relates to vehicle structures. More particularly, the subject matter relates to a roof structure for a vehicle made of a lattice structure adapted to join top portions of door openings and of an outer shell.
2. Description of Related Art
Whether it is a rail vehicle, an aircraft or a bus, the structures of long mass transit vehicle are often designed in a similar fashion: ribs are placed along the length of the vehicle and are wrapped with an exterior skin. For ease of construction, the vehicle structure is typically made of a floor, two side walls and a roof and two end caps.
The roof structures of such vehicles are typically made of either parallel ribs covered by the exterior skin or covered by open extrusions, longitudinally extending closed extrusions or a sandwich structure. However, none of these structures is optimized for stress loads on the vehicle and are therefore heavier than necessary.
There is therefore a need for an improved roof structure for a vehicle.